As a digitized radiation detector for medical use, dental use, non-destructive inspection use, or the like, a detector using a system in which incident X-ray is once converted to visible light by a scintillator layer is the mainstream. In the scintillator layer, several types of materials are used, however, in a flat panel detector (hereinafter abbreviated as “FPD”) for medical use, a device using a dental CMOS sensor, or a CCD-DR device for medical use/animal diagnostic use, thallium-activated cesium iodide (hereinafter abbreviated as “CsI/Tl”) is used in many cases.
A CsI/TI phosphor layer can be easily formed into a planar shape by a vacuum vapor deposition method. Moreover, by properly adjusting the deposition conditions, a film having a structure in which fiber crystals (column crystals) having a diameter of about 5 μm are arranged can be formed. By forming such a fiber structure, due to a difference in refractive index between the CsI crystal (refractive index=1.8) and a gap between the crystals (refractive index=1), fluorescence converted from radiation in one certain fiber reaches a surface of a sensor at a position which is not much deviated to a surface direction from the light emitting point. As a result, as a radiation image detecting device, a image which is not much blurred is obtained. That is, by forming the CsI/Tl phosphor layer under proper conditions, the CsI/Tl phosphor layer can simultaneously have a scintillation function to convert radiation to visible light and a fiber plate function to hold an image to the next sensor section.
A digital image detecting device for radiation images generally has a 17 inch (430 mm) square size in many cases. Even if the device has a smaller size than that, in response to the increase in the number of the devices accompanying the recent popularity of the digital devices, there is a tendency that many small-sized sensor panels are arranged in a vacuum vapor deposition device, and phosphor layers are formed at a time. Due to this, the size of the vacuum vapor deposition device and crucible is increased.